Treatment of Parkinson's disease in Japan

In this paper, the course of therapy for Parkinson's disease is outlined. The rationale for the use of DA-receptor-agonist (DA agonist) monotherapy or early combination therapy using levodopa and a DA agonist is that these therapies are asociated with a lower incidence of motor complications. However, the disease progresses, the use of levodopa in combination with a DA agonist results in motor complications and development of levodopa dependency in parkinsonian patients, because the effect of levodopa on parkinsonism is very strong. In this study, a positive correlation between the Hoehn-Yahr severity score at off-periods and duration of illness was observed in parkinsonian patients with long duration of illness. This indicates that responsiveness to dopaminergic therapy still exists even in patients in advanced stages of Parkinson's disease, indicating that continuous stimulation of DA receptors and reducing the excessive fluctuation in the plasma levodopa level possibly improve motor complications. If the dose of the DA agonist is simply increased without reduction of levodopa doses, dyskinesia worsens. Although levodopa therapy is essential in the case of patients in advanced stages of Parkinson's disease, the therapeutic principle, which depends on levodopa efficacy, must be changed. Reduction of the levodopa dose and administration of a sufficient dose of a DA agonist, which is equivalent to levodopa dose reduction, is one of the possible means of effective therapy of the disease.